Crushing rolls



P. M. M KENNA CRUSHING ROLLS June 23, 1964 2 Sheets-Shes INVENTOR.P/V/A/P M. MckE/V/VA United States Patent 3,138,338 CRUSHING ROLLSPhilip M. McKenna, Greensburg, Pa., assignor to Kennametal Inc.,Latrobe, Pa., a corporation of Pennsylvania Filed May 29, 1961, Ser. No.113,307 6 Claims. (Cl. 241-494) This invention relates to thecomposition, structure, and arrangement of crushing rolls for use inconventional crushing equipment for the size reduction of variousmaterials.

One conventional type of crushing equipment uses two cylindrical rolls,each comprising a solid cylindrical core of tough steel and a removableouter shell of hard steel that is intended to resist abrasion.Generally, one of the rolls is adjustable relative to the other and issupported on strong springs. The material to be crushed is fed in astream between the rolls, the crushing capacity of which is proportionalto their peripheral speed. Heretofore, it has not been practicable tooperate crushing rolls at high speeds, because at higher speeds slippageoccurs between the rolls and the feed, resulting in abrasive action thatwears the rolls very rapidly. Even at lower speeds, there is appreciablewear, which is not uniformly distributed throughout the length of therolls but tends to be concentrated at different points, with the resultthat grooves are worn in the rolls at those points, diminishing theirefficiency and producing material that is less uniformly sized; and thisgrooving effect increases as the speed of the rolls increases.

It is among the objects of this invention to provide a crushing roll orrolls for use in conventional crushing equipment of various types thatwill overcome the foregoing difilculties and that can be operated atvery high peripheral speeds without substantial abrasion or grooving ofthe roll surfaces.

Another object is to provide a crushing roll or rolls that may beoperated at such high peripheral speeds that crushing efliciency isgreatly increased by the inertia of the roll itself when rotating atsuch speeds.

A further object is to provide a composite crushing roll having an outershell of very hard metal of high density supported by a thin-walledsleeve of resilient material on a central drive shaft, which can berevolved at a sufficiently high speed to enable the roll to resist theforces of crushing in a resilient manner by the inertia of the heavyouter shell and, because of the hardness of that shell, withoutsubstantial abrasion or grooving of the roll surface.

A still further object is to provide an improved composite crushing rollthat fulfills the foregoing objectives and, in addition, can be used ina conventional crushing machine either with an opposed roll of the sametype or an opposed roll of conventional design; in the latter case, thecharacteristics inherent in the improved composite roll being such thatthey will effectively prevent or substantially reduce the tendency ofthe opposed conventional roll to acquire a grooved surface whenoperating at conventional and higher speeds.

Other objects of the present invention will be apparent fro m thefollowing description of a preferred embodiment in connection with theaccompanying drawings, in which:

FIG. 1 is a front elevation, partly in section, of the composite roll ofthis invention;

FIG. 2 is a fragmentary front elevation, insection, of the roll shown inFIG. 1, with the wedge rings supporting the outer shell shown in theirinitial positions before final assembly of the roll;

FIG. 3 is an end elevation, on a reduced scale, of the roll shown inFIG. 1;

FIG. 4 is a diagrammatic end elevation of a conven- Patented June 23,1964 tional roll crusher, in which are mounted two opposed compositerolls made in accordance with the present invention;

FIG. 5 is a diagrammatic end view of two opposed rolls adapted for usein the crusher of FIG. 4, one of said rolls being of the composite typeof this invention and the other being a conventional roll; and

FIG. 6 is a modification of FIG. 5, in which the conventional roll is oflarger diameter than the composite roll, the rolls being adapted for usein a conventional crusher of larger size than that shown in FIG. 4.

The crushing roll of this invention comprises an outer shell of hardmetallic composition, preferably cemented tungsten carbide or the like,having a specific gravity greater than 10 and a Youngs modulus ofelasticity at least twice that of steel. The shell has a cylindricalouter surface and opposed double frustro-conical inner surfaces. Theshell is supported on a central shaft by a pair of wedge rings, theinner surfaces of which are cylindrical and fit the shaft snugly and theouter surfaces of which are tapered to conform to the taper of the innersurfaces of the shell. Between the inner surfaces of the shell and theouter surfaces of the wedge rings is a thin layer or sleeve of resilientmaterial that is preferably under radial compression in the assembledroll. This composite roll is adapted to be used in conventional rollcrushers of various types either opposed to a similar roll or opposed toa conventional roll. In the latter case, it may be advantageous in somecases to have the conventional roll of larger diameter and to rotate itat a lower speed than the other roll.

Referring to the drawings, the improved composite roll A of thisinvention includes a cylindrical shaft 1, preferably of tough steel,with a central portion 2 terminating in shoulders 3. Mounted'on thecentral portion of this shaft are two wedge rings 4 and 5, alsodesirably of tough steel. The combined axial length of these rings issomewhat less than the length of the central portion of the shaft. Therings are machined to a snug fit on the shaft, and their outercircumferential surfaces 6 are tapered uniformly so that the adjacentinner ends 7 of the rings are of smaller diameter than the outer ends 8.

Roll A also includes an outer shell 11, preferably of cemented tungstencarbide or similar material having a specific gravity that is greaterthan 10 and a Youngs modulus of elasticity that is more than twice thatof steel. The shell has a cylindrical outer surface 12 and opposed,

uniformly tapered inner surfaces 13 and 14, such that the insidediameter of the shell at the center is less than its inside diameter atthe ends. To avoid strains, a portion of the central inner surface 15 ofthe shell is preferably cylindrical, so that the shell has opposed,double frustroconical inner surfaces that have the same angle of taper,

preferably about 10, as the outer circumferential surfaces of the Wedgerings; and these inner surfaces are separated by a short cylindricalsurface. The shell is desirably as long as the central portion 2 of theshaft 1. The tapered inner surfaces of the shell are slightly larger indiameter than the corresponding portions of the wedge rings when theends of those rings are flush with the ends of the shell. The resultingannular space between the wedge rings and the shell is filled withresilient material 16, such as rubber, that is preferably under radialcompression in the final roll assembly.

In assembling the composite roll, the shell is placed over the centralportion of the shaft and supported more or less concentricallytherewith. The wedge rings, with a sleeve of resilient rubber bonded onthe outer surface of each ring, are then placed over the shaft from eachend and their inner ends are pushed together towards the center of theshell. FIG. 2 shows the approximate position of the wedge rings whenthey have been pushed in place far enough that the rubber layer 16,without being compressed, fills the tapered annular space between therings and the shelll. For drawing the rings further into the shell andthereby subjecting the resilient material to radial compression, therings may conveniently be provided with a plurality of longitudinalholes 17, parallel to the axis of the roll. Through these holes, whenthey are aligned, may be passed rods 18 with threaded ends. Bytightening nuts 19 on the ends of these rods, the wedge rings may bedrawn axially inward towards the center of the roll until the rubbersleeves have been subjected to the desired degree of compression, whichwill generally occur when their thickness has been reduced by about 50percent, depending on the characteristics of the resilient materialused. For example, with a 12-inch long roll having an overall diameterof 12 inches and having the wedge rings tapered at an angle of it hasbeen found satisfactory to use a rubber sleeve having a thickness ofabout 3 of an inch before it is compressed. After the wedge rings havebeen pressed into the shell, the outer ends of the rings wil be flush,or can be machined flush, with the ends of the shell and the shoulders 3on the shaft. If desired, the rings may then be secured to the shaft bywelding as at 21 (see FIG. 1) and the rods 18 removed.

The resilient rubber sleeve 16 between the wedge rings and the shellcompensates for the greater coefficient of thermal expansion of thesteel wedge rings, which is two and one-half to three times that of thetungsten carbide shell. Without such a resilient layer, the shell wouldtend to rupture as the roll became heated in use. The resilient layeralso permits the roll to resist the shocks and forces of crushing in aresilient manner not only by its own cushioning effect, but also (due toits substantial confinement between the shell and the wedge rings) byacting in the manner of a hydraulic fluid to distribute the localizedshocks of crushing to other portions of the roll.

It is a feature of the composite roll of this invention that it can berotated at very high surface speed during the crushing operation.Because of the hard surface of the tungsten carbide outer shell, suchspeeds do not cause appreciable wear or grooving of the roll surface, asthey do with conventional steel rolls alone.

A great advantage of such higher speed is that the capacity of a set ofrolls is increased several times that attainable by steel rolls of equalsize rotated at lower peripheral speeds. In other words, using thecomposite rolls of this invention, a crushing machine of a given sizecan do the work of a much heavier and larger machine using conventionalrolls. This advantage is of considerable importance wherever thetransport of crushing machines to remote sites is involved, as, forexample, at distant mines for crushing ore or at remote airfields forcrushing ballast to dress the field.

The composite roll of this invention may be used in various combinationsand arrangements in conventional roll crushing equipment. For example,as shown in FIG. 4, two of these rolls A and A may be used in aconventional two-roll crusher 30. Roll A is mounted on fixed bearings.Roll A is resiliently mounted in a conventional manner on a bearingbracket 31, one end of which is pivotally mounted at 32 to the base ofthe crusher and the other end of which is resiliently supported bysprings 33. This arrangement permits throat 34 between the rolls to openup against the urging of springs 33 when an unusually hard lump ofmaterial to be crushed enters the slot between the rolls. It has beenfound that the composite rolls of this invention possess inherentprotective features in addition to the cushioning and distributiveeffects of the reslient layer that have been mentioned above. Since thecarbide shell has a density nearly twice that of steel and since it ismounted on the outer periphery of the roll and is rotated at a very highspeed (that would be destructive of opposed steel rolls), it possessesexceptionally high rotational inertia compared to a conventional steelroll. When an unusually hard or tough lump of feed material enters theslot between two such composite rolls, and not in the exact center ofthat slot, the forces generated tend not only to open the slot but alsoto open one end more than the other. Such twisting forces on the shellare resisted in a resilient manner by its rotational inertia, which islarge enough to have a pronounced gyroscopic and centering effect. Thisgyroscopic reaction of the shell is much more prompt than the reactionof the supporting springs 33, so that the initial shock of impact hasless chance of damaging the rolls than when the protective action of thesprings alone is relied upon. In addition, the high density of thecomposite roll of this invention (as compared to conventional crushingrolls of the same size) is equivalent to a large inertia that yieldablyresists displacement of the rolls in any direction.

A further advantage of the roll arrangement in FIG. 4 is that, with twoopposed carbide surfaced rolls, their wear is so negligible that theycan be used to crush various materials without serious contamination byworn-off particles of the rolls, thus permitting the economies of rollcrushing not heretofore even possible because of the excessive wear ofconventional crushing rolls even at low speeds.

In addition, it has been found that when the composite roll of thisinvention is used with an opposed steel roll of conventional design, theperformance of the latter is unexpectedly improved. Where, as in FIG. 5,both rolls are of the same diameter and are rotated at the same speed (aspeed well above that which would cause grooving of two opposed steelrolls), the composite carbide roll A unexpectedly performs a truingfunction that entirely prevents or greatly reduces grooving of theopposed steel roll B. A possible explanation of this phenomenon mayreside in the fact that, at the high speeds at which the rolls rotate,there is considerable slippage between the material that is fed betweenthe rolls and the rolls themselves. The resulting abrasive action, whichinevitably causes grooving where two opposed steel rolls are used,results in a dressing or truing action when one of the rolls is acomposite carbide roll of this. invention and the other a steel roll.Because the carbide roll itself is not substantially affected by theabrasive action of the feed and does not itself become grooved, the feedis more or less evenly distributed between the rolls and tends to avoidgrooving the steel roll; or, if such grooves are started, they tend tobe eliminated by the dressing or truing action referred to. Theadvantage of this type of arrangement, in which the composite carbideroll is opposed by a conventional steel roll, is that many of thebenefits pointed out above of two carlbide rolls are obtained at thecost of a single such rol In addition, the carbide roll of thisinvention can be used, as shown in FIG. 6, with a conventional steelroll of larger diameter. In this arrangement, the carbide roll A ismaintained at a sufficiently high speed to obtain the inertialadvantages previously referred to, while the steel roll C (about 2 /2times the diameter of A) is preferably rotated at a lower peripheralspeed. The surface speed differential between the rolls produces a shearing stress on the material being crushed, which in many cases isadvantageous to and facilitates the crushing operation. In other words,the material fed between the rolls is subjected not only to a crushingforce as in conventional rolls but also to a differential shearingaction that helps to disintegrate the material. Apparently, the feedmaterial in the throat of the rolls is subjected to a high concentrationof crushing forces by the smaller, incisive composite roll A, while atthe same time the feed is held back, in effect, by friction with theslower moving steel roll. As a result, lumps of feed material are brokenwith less expenditure of force than if both rolls were of large size.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. A crushing roll comprising an outer shell of hard metalliccomposition having a specific gravity greater than ten and having aYoungs modulus of elasticity at least twice that of steel and having asubstantially lower coeflicient of thermal expansion than steel, theshell having opposed double frustro-conical inner surfaces taperingradially inwards towards the center of the shell, a shaft concentricwith the shell, a pair of steel Wedge rings mounted on the shaft, eachring having a frustro-conical outer circumferential surface conformingto an inner surface of the shell, and a layer of resilient materialbetween the tapered surfaces of the rings and shell to yieldablycompensate for the difference in the coefficients of thermal expansionof the steel wedge rings and the shell.

2. A crushing roll according to claim 1, in which the outer shell ismade of cemented tungsten carbide.

3. A crushing roll according to claim 1, in which the resilient materialis radially compressed between the tapered surfaces of the rings andshell.

4. A composite crushing roll comprising a cylindrical shaft, a pair ofsteel wedge rings mounted on the shaft with their inner ends spaced fromeach other, the outer circumferential surfaces of the rings beingtapered inwardly from their outer ends towards their inner ends, a thinwalled sleeve of resilient material mounted on the taperedcircumferential surface of each ring, and an outer shell of cementedtungsten carbide having two tapered inner surfaces each conforming intheir angle of taper to the tapered surface of a different wedge ring,the resilient sleeves being under radial compression between the taperedsurfaces of the rings and shell to yieldably compensate for thedifference in the coeflicients of thermal expansion of the steel wedgerings and the tungsten carbide shell.

5. A crushing roll according to claim 4, in which the sleeve is rubberand is compressed to about one-half of its original thickness.

6. A crushing roll according to claim 4, in which the angle of taper ofthe wedge rings is approximately ten degrees.

References Cited in the file of this patent UNITED STATES PATENTS488,867 Brennan Dec. 27, 1892 1,681,868 McLean Aug. 21, 1928 2,020,157Myers Nov. 5, 1935 2,065,471 Krider Dec. 22, 1936 2,167,544 De Bats etal. July 25, 1939 2,332,071 Gordon Oct. 19, 1943 2,474,625 Cerow June28, 1949 2,563,266 Penigault Aug. 7, 1951 2,800,959 Baker et al. July30, 1957 2,803,411 Pollitz Aug. 20, 1957 FOREIGN PATENTS 434,971 GreatBritain Sept. 12, 1935

1. A CRUSHING ROLL COMPRISING AN OUTER SHELL OF HARD METALLICCOMPOSITION HAVING A SPECIFIC GRAVITY GREATER THAN TEN AND HAVING AYOUNG''S MODULUS OF ELASTICITY AT LEAST TWICE THAT OF STEEL AND HAVING ASUBSTANTIALLY LOWER COEFFICIENT OF THERMAL EXPANSION THAN STEEL, THESHELL HAVING OPPOSED DOUBLE FRUSTRO-CONICAL INNER SURFACES TAPERINGRADIALLY INWARDS TOWARDS THE CENTER OF THE SHELL, A SHAFT CONCENTRICWITH THE SHELL, A PAIR OF STEEL WEDGE RINGS MOUNTED ON THE SHAFT, EACHRING HAVING A FRUSTRO-CONICAL OUTER CIRCUMFERENTIAL SURFACE CONFORMINGTO AN INNER SURFACE OF THE SHELL, AND A LAYER OF RESILIENT MATERIALBETWEEN THE TAPERED SURFACES OF THE RINGS AND SHELL TO YIELDABLYCOMPENSATE FOR THE DIFFERENCE IN THE COEFFICIENTS OF THERMAL EXPANSIONOF THE STEEL WEDGE RINGS AND THE SHELL.